WO2008002164A1

WO2008002164A1 - A method and system for wireless transfer of electrical power

Info

Publication number: WO2008002164A1
Application number: PCT/PL2007/000043
Authority: WO
Inventors: Piotr Musial
Original assignee: Piotr Musial
Priority date: 2006-06-28
Filing date: 2007-06-25
Publication date: 2008-01-03

Abstract

The method of wireless transfer of electrical power, consisting in inducing the inductive elements of the transmitter with an electric signal in order to produce a magnetic field, which generates electrical energy in the inductive element of the receiver coupled with it. In the transmitter (N) a matrix is formed made up of identical induction cells (CI) mutually connected in rows and columns, where detected is the position of the inductive elements (EI) of the receivers (O) placed on the transmitter (N), and where the induction cells (CI) of the transmitter lying underneath are stimulated by electrical excitation of the proper columns and rows in the matrix. The system for wireless transfer of electrical power composed of a transmitter and the inductively coupled with it receiver, where the transmitter is made up of many induction cells, a source of power, and control elements. The induction cells (CI) in the transmitter (N) are interconnected forming a matrix whose rows and columns are connected via switch keys (P) to the source of power and the control-and-driving block (K), which is connected to the induction cell selection block (W).

Description

A method and system for wireless transfer of electrical power

The gist of the invention is a method of wireless transfer of electrical power and a system realising such transfer. The prime application of the solution is to supply power to laptops in conference or lecturing halls, etc. without any of the limitations affecting the time and volume of the energy consumed, which are experienced when power supply is provided from power cells. The solution can also be used to supply power to various kinds of other portable equipment which require to be fed power, and to charge cells and/or batteries.

Together with the development and ever increasing number and variety of portable devices which require the supply of electrical energy finding a solution to the problem of providing the supply in the possibly most effective and most user- convenient way is growing in significance. Long known has been the method of feeding power from cells and batteries of various designs and capacities. However, because of their limited life, cells require frequent replacement or recharging. Meanwhile, in the case of such devices as portable computers and other equipment based on computer technology, the ever new applications developed, particularly of the multimedia type, carry the need for increasing power consumption, which frequently requires feeding from the mains, hence turns them into stationary devices. Another acute inconvenience of supplying power by direct electrical contact between the receiver and the source of power consists in the sensitivity of electrical contacts to the ambient conditions, e.g. humidity. The above inconveniences are eliminated by the methods and devices for wireless transfer of electrical energy via a magnetic stream, Le. inductive coupling of the elements of the transmitter and receiver.

From the publication entitled; Power transmission of a desk with a cord- free power supply, IEEE Transactions on Magnetics, Vol. 38, No. 5, September 2002, a method is known to transfer electrical energy in a contact-less manner, based on electromagnetic induction. On a plane many inductive elements, i.e. coils arranged in various configurations side by side are placed not connected with one another. Each is connected with a separate source of power and induced independent of the others so as to produce a magnetic field. Over the coils, which form the transmitter, a winding of a larger diameter is placed forming the receiver which covers several coils of the transmitter. By inducing the selected coils of the transmitter and shifting the receiving coil in relation to the coils of the transmitter the power induced in the receiver and transfer efficiency is measured, and on this basis the optimal positioning of one to the other and the active surfaces of the coils are identified.

From the description of the patent application US6906495 the method of transmitting electrical power is known through coupling of the inductive elements, where on the surface of the transmitter windings are placed shaped so as to generate a magnetic field whose lines are substantially parallel to the plane of the transmitter and can rotate. The perimeter of the transmitter's active area is large enough to embrace the winding of the receiver in any of its parallel orientations to the active area of the transmitter.

From the description of the patent application WO2005024865 a method is known to transfer energy through electromagnetic induction, which consists hi appropriate shaping of the magnetic field with a winding stretching horizontally over the entire active surface of the transmitter, and an additional screen.

From the description of the patent application US6906495 a system for cordless transfer of electrical power is known consisting of a transmitter and a receiver inductively coupled with it. The transmitter has two windings controlled and powered independently, and a control circuit, and the receiver contains an inductive element and a rectifier.

In the description of the patent application EP1275208 a system is disclosed for wireless transfer of energy, whose transmitter is composed of a series of inductive elements in parallel connection configuration, connected to the source of power equipped with a control element. In the system there are several independent receivers, each with an inductive element coupled with one of the inductive elements of the transmitter. The system can also include additional elements which enable the transfer of additional signals, e.g. via magnetic paths not used for transmitting the electrical energy.

The disadvantage of the known methods and devices for cordless transfer of energy is high dependence of the transfer efficiency on the mutual positioning of the transmitter's and receiver's inductive elements, or an excessively strong magnetic field emitted by the transmitter beyond the active surface of the receiver. The solutions eliminating both these disadvantages are, on the other hand, so complex that the costs of their implementation render their broad practical application impossible.

The method of wireless transfer of electrical power consisting in inducing the inductive elements in the transmitter with an electrical signal so as to produce a magnetic field which, in the inductive element of the receiver, coupled with it, generates electrical energy is, as claimed in this invention, characterised by the provisions that in the transmitter a matrix is formed made up of identical induction cells mutually connected in rows and columns, the location of the inductive elements of the receivers, placed on the transmitter is detected, and the induction cells of the transmitter underneath are stimulated by applying electrical excitation to the appropriate columns and rows in the matrix.

The excitation of the selected induction cells is effected by switching the respective columns and rows in the matrix to one of the four states: "disconnected", "common", "stimulus +", and "stimulus -".

In the event more than one receiver is detected, the respective induction cells in the transmitter are stimulated one after another at intervals.

La the event more than one receiver is detected in the same column or row, the respective induction cells in the transmitter are stimulated all at the same time.

It is advantageous for the positions of the receivers on the transmitter to be detected using the same induction cell matrix by initial simultaneous stimulation of all or selected induction cells with a low power impulse.

The system for wireless transfer of electrical power, composed of a transmitter and inductively coupled receiver, where the transmitter contains many induction cells, a source of power, and control elements is, as claimed in the invention, characterised by the fact that the induction cells in the transmitter are mutually interconnected creating a matrix whose rows and columns are connected via switch keys to the source of power and a control-and-driving block. The control-and-driving block is also connected to the induction cell selection block.

The rows and columns of the matrix are connected to the common source of power and a common control-and-driving block.

Advantageous is such a version of the system where all rows and columns of the matrix are connected to the same source of power and control-and-driving block.

The rows of the induction cell matrix are connected to one voltage pole through the switch keys controlled from the control-and-driving block via a demultiplexer of the rows. The columns of the induction cell matrix are connected to the other voltage pole through the switch keys controlled from the control-and-driving block via the column demultiplexer and a programmable generator.

Particularly advantageous features are demonstrated by the system where an induction cell of the transmitter is composed of coils in parallel connection and a condenser forming the resonating circuit, and the there connected semi- conductive blocking element.

All induction cells in the matrix are identical.

In one of the system variants the blocking element in the induction cell which contains a resonating circuit takes the form of a diode.

In the advantageous variety of the system, in the transmitter, between the matrix columns and the control-and-driving block, a signal measuring block is interposed.

Power transistors serve as the keys switching the columns and rows in the matrix.

In the most advantageous version of the system the control-and-driving block is realised in the form of a programmed microprocessor control.

The solution, as claimed in the invention, ensures that the effectiveness of electrical power transfer is made independent of the receiver's position on the surface of the transmitter. It also enables minimising the dimensions of the energy receiver while retaining maximum achievable efficiency, as its size is similar to that of a single cell in the transmitter. The realisation of the transmitter in the form of a controlled matrix of inductive elements, where emission is induced from only the selected element placed directly under the transmitter, ensures minimization of the undesirable magnetic radiation, since the emission of the magnetic field takes place only directly under the receiver. At the same time, thanks to making use of multiplexing the rows and columns in the matrix, the number of the components and connections in the transmitter is reduced, since all the inductive elements can make use of a common power source and control system.

The solution is explained fuller in the example illustrated with a drawing, where Fig. 1 presents, in a schematic way, the general concept of the solution, Fig. 2 presents the structure of the inductive element matrix and their switching, and Fig. 3 presents the block diagram of the transmitter system.

The method of wireless transfer of the electric power makes use of the phenomenon of electromagnetic induction, and its general idea consists in transferring electrical energy from transmitter N to receiver O via a magnetic stream SM. The transmitter N, which is the source of power, is built so that its whole surface available for use is covered with induction cells CI, which, in the simplest version, can be single inductive coils. The induction cell can also be made of more complex circuits, e.g. of the resonance type. The cells are arranged in columns A, B, C, D, and rows 1, 2, 3, 4, and connected together so that they create a regular matrix. Each column and row of the matrix can be switched into one of the four states: "disconnected", "common", "stimulus +", and "stimulus -" with controlled switches P. By switching the selected column and row to "stimulus +" and "stimulus -", respectively, induction is caused of the induction cell CI lying at their crossing. Using additional switches DP one can realise any desirable combination of the connections between the columns and rows in the matrix and the source of power, hence stimulate any selected induction cells CI at the same time or consecutively. Once the receiver O, also equipped with an induction element EI, is placed on the surface of the transmitter N, its position is detected through initial simultaneous stimulation of all induction cells CI in the matrix of the transmitter N with a low power impulse. This is done by switching all columns and rows into the "common" position and at the same time connecting the common rail to the "stimulus +" for columns and "stimulus -" for rows using the additional switches DP. The initial stimulation produces minor energy, which is sufficient to start the receiver O and initiate communication with the transmitter N. The position of the receiver can also be detected in any other way, e.g. using a separate circuit. Having detected the position of the receiver O and selected the induction cell CI in the transmitter N, coupled with an inductive element EI of the receiver O, i.e. the one lying underneath, the rows and columns in the matrix are switched so that the electrical stimulation is tied to the row and column at the crossing of which the appropriate induction cell CI is located. If more than one receiver is detected, the relevant induction cells are stimulated one after another at time intervals. Considering that within any given unit of time a limited amount of energy can be transmitted, the maximum number of the receivers is limited by the minimum power that needs to be supplied to them. If, for example, on the matrix shown on Fig.2 and composed of 16 induction cells CI arranged in four rows 1, 2, 3, and 4, and four columns A, B₅ C, and D, two receivers are detected placed over the induction cells located at the 2B and 4C crossings, first the induction cell 2B, then the induction cell 4C, is stimulated for some time, whereupon the cycles is repeated. In the event that the selected induction cells CI to be stimulated are located in the same column or row, they can be stimulated simultaneously, e.g. induction cells 2 A and 2C, by parallel switching of row 2 to the state of "stimulus +" and columns A and C to the state "common" while simultaneous switching the additional DP switch to the "stimulus — " state. The control of all switches, i.e. stimulation of the appropriate induction cells, is performed automatically via a programmed microprocessor circuit.

The system for wireless transfer of electrical power is composed of the transmitter N and the inductively coupled receiver O. The system of transmitter N is composed of a set of identical induction cells CI, the corresponding number of switch keys P, two demultiplexers DR, DK, a programmable generator G, an induction cell selection block W, a signal measuring block S, a control-and- driving block K, and a power feeder Z. A single induction cell CI is made up of a coil L and a condenser C, connected parallel and forming a resonating circuit together with the semiconductor blocking element D in the form of a diode connected to it. AU induction cells CI are connected with one another in rows and columns so that they form a matrix. Each row of the induction cells CI in the matrix is connected via a switch key P to the high voltage pole of the power fed and to the row demultiplexer DR controlled from the control-and-driving block K. Each column of the matrix, on the other hand, is connected via the switch key P with the ground and the column demultiplexer DK controlled from the control- and-driving block K and the programmable generator G. In addition, between the columns of the induction cell CI matrix and the monitoring control-and-driving block K a signal measuring block S is interposed in the back coupling loop. The block is composed of an analogue multiplexer MA, high-pass filter F, rectifier PR, and an analogue-digital transducer AC. In the exemplary realisation MOSFET power transistors are used as the switch keys P. These are controlled from the programmed microprocessor control unit which constitutes the control-and- driving block K₅ via the transistor bridge control circuits, e.g. L6386, which adjust the logical signals to the levels acceptable by the microprocessor. To serve as demultiplexers integrated circuits CMOS4014 are used and an AD9832 circuit is used as the programmable generator. In the exemplary realisation the resonance frequency of the induction cell CI is 100 kHz, the inducing signal is 200 V, and the power processed by the receiver is 10OW.

Once the receiver O is placed on the surface of the transmitter N, its position is detected in any way by the induction cell selection block W, and identified is the column and row at the crossing of which lies the induction cell CI of the matrix under the inductive element EI of the receiver, which should be induced. The selected induction cell CI is stimulated by opening of the switch key P of the identified row, and the cyclicaj opening and closing, i.e. shorting to the ground, of the switch key P relevant for the identified column. The signal of the appropriate frequency equal to the resonance frequency of the induction cell is digitally generated in the programmable generator G controlled by the microprocessor control K. The frequency can be adjusted to the changing load and altered to compensate for any lack of precision in the mounting. The exact value of the resonance frequency for each induction cell CI is determined through measurement in the process of producing and storing in the memory of the microprocessor control K. The microprocessor control K activates the appropriate keys of the row and column through transmitting the relevant addresses to the demultiplexer of the row DR and the demultiplexer of the column DK. The diode D blocks the flow of the current from the stimulated induction cell to the other induction cells preventing their undesirable self-excitation. The quality of the stimulation is controlled in the signal measuring block S by gauging the signal amplitude on the transistor drain which serves as the switch key P of the selected column. The signal generated by the stimulated element of the matrix is filtered, rectified, and measured with an analogue-digital transducer, where it is read by the microprocessor control K and used in the algorithm controlling the induction cell.

Claims

1. The method of wireless transfer of electrical power, consisting in inducing the inductive elements of the transmitter with an electric signal in order to produce a magnetic field, which generates electrical energy in the inductive element of the receiver coupled with it, is characterized by the provision that in the transmitter (N) a matrix is formed made up of identical induction cells (CI) mutually connected in rows and columns, where detected is the position of the inductive elements (EI) of the receivers (O) placed on the transmitter (N), and where the induction cells (CI) of the transmitter lying underneath are stimulated by electrical excitation of the proper columns and rows in the matrix.

2. The method as in Claim 1 characterised in that the excitation is effected by switching the appropriate columns and rows of the matrix to one of the four states: "disconnected", "common", "stimulus +", "stimulus — ".

3. The method as in any of Claims 1 - 2 characterised in that upon detection of more than one receiver (O), the respective induction cells (CI) of the transmitter (N) are stimulated one after another at intervals.

4. The method as in any of Claims 1 - 3 characterised in that upon detection of more than one receiver (O) lying in the same column or the same row, the respective induction cells (CI) of the transmitter (N) are stimulated all at the same time.

5. The method as in any of Claims 1 - 4 characterised in that the position of the receivers (O) on the transmitter (N) is detected by the matrix of induction cells (CI) through an initial simultaneous stimulation of all or selected induction cells (CI) with a low power impulse.

6. The system for wireless transfer of electric power, composed of a transmitter and the inductively coupled with it receiver, where the transmitter is made up of many induction cells, a source of power, and control elements, is characterised by the fact that the induction cells (CI) in the transmitter (N) are interconnected forming a matrix whose rows and columns are connected via switch keys (P) to the source of power and the control-and-driving block (K), which is connected to the induction cell selection block (W).

7. The system as in Claim 6 characterised in that the rows and columns of the matrix are connected to the common source of power and a common control-and-driving block (K).

8. The system as in Claim 7 characterised in that all rows and columns of the matrix are connected to the common source of power and a common monitoring-control-and-driving block (K).

9. The system as in any of Claims 6 - 8 characterised in that the rows of the induction cell (CI) matrix are connected to one voltage pole via switch keys (P) controlled from the control-and-driving block (K) via a row demultiplexer (DR), and the columns of the induction cell (CI) matrix are connected to the second voltage pole through switch keys (P) controlled from the control-and-driving block (K) via a column demultiplexer (DK) and a programmable generator (G).

10. The system as in any of Claims 6 - 9 characterised hi that the induction cell (CI) is composed of coils in parallel connection (L) and a condenser (C), forming the resonating circuit, and the there connected semi- conductive blocking element (D).

11. The system as hi Claim 10 characterised in that all induction cells (CI) are identical.

12. The system, as in Claim 10 or 11 characterised in that a diode (D) plays the function of the blocking element.

13. The system as in any of Claims 6 - 12 characterised in that between the matrix columns and the control-and-driving block (K) a signal measuring block (W) is interposed.

14. The system as hi any of Claims 6 - 13 characterised in that power transistors serve as the switch keys (P).

15. The system, as in any of Claims 6 - 14 characterised in that the control- and-driving block (K) is a programmed microprocessor control.